Underground storage cavern with damage-proof tubing

ABSTRACT

An underground storage cavern suitable for the storage of fluids such as hydrocarbons or ammonia is normally penetrated by a tube through which a second fluid can be admitted to the cavern for the purpose of displacing the stored fluid. This tube can be protected from damage caused by cave-ins by surrounding the tube with a mound of comminuted material such as crushed rock.

[ Apr. 16, 1974 United States Paten-t [191 Hendrix Q UNDERGROUND STORAGE CAVERN WITH DAMAGE-PROOF TUBING 6/1971 Block...................... 12/1962 Warren........

3/ 1960 Kenneday e n v. a L 0 4 9 l 2 [75] Inventor: Hurshel V. Hendrix, Bartlesville, Okla.

[73] Assigneer Phillips Petroleum Company,

6 k P w P 4 3 9 H 1 a l [22 Filed:

ABSTRACT [21] App]. No.: 287,250

An underground storage cavern suitable for the stor- 52 US. 61/.5, 166/278 age 0f fluids Such as hydrocarbons ammmlia is 51 Int.

mally penetrated by a tube through which a second fluid can be admitted to the cavern for the purpose of [58] Field of Search displacing the stored fluid. This tu from damage caused by cavetube with a mound of comminute k c O r d e h S u r c s T N m MA .1? mm mm e MW e D E H N U m U 3,708,013 1/1973 Dismukes..............................166/51 3,704,593 12/1972 8 Claims, 3 Drawing Figures 1 UNDERGROUND STORAGE CAVERN WITH DAMAGE-PROOF TUBING BACKGROUND OF THE INVENTION This invention relates to the storage of fluids in underground storage caverns. In another aspect, this invention relates to a method of protecting a tube extending into an underground cavern from damage caused by debris falling from the ceiling of the underground cavern.

It is common practice to provide underground storage caverns for hydrocarbons, ammonia, and other fluids. Typically, these caverns are formed in a soluble formation such as a salt bed. In dissolving the salt or otherwise forming the cavern, a certain amount of insoluble debris accumulates at the bottom, for example, from pieces of shale or anhydrite which may be present in the soluble formation. After formation of the cavern, additional debris continues to fall from the ceiling. Often, the debris amounts to a major cave-in and can sever or otherwise damage the tubing utilized for introducing and removing a second fluid, usually a liquid, which is used to displace the stored fluid from the cavern. If severed or damaged severely enough, a new tube must be introduced into the cavern. Since thetubing can not be lowered below the top of the debris, a loss of storage space results represented by the voids within the layer of debris. Also, it has not been possible to re- -cover the material accumulating within these voids,

whether it be stored fluid or displacement fluid.

SUMMARY OF THE INVENTION It is the object of this invention to provide an underground cavern for storage of fluids that is protected against damage to a production tube extending into the cavern by falling debris. In accordance with the object of this invention, crushed rock or other suitable comminuted material is introduced into the cavern so as to form a protective mound about the production tube. The mound shields the tube against falling debris.

, BRIEF DESCRIPTION oa nE DRAWING DESCRIPTION OF THE PREFERRED EMBODIMENTS The following detailed description will serve to better illustrate the invention.

Referring now to FIG. 1, there is shown an underground cavern 10. The cavern can be one obtained as by dissolving salt or other soluble material from a formation. The cavern can also be a natural cavern. Communication with the surface 12 is provided by means of a casing 14 which is shown inserted into drilled hole 16. The annular space between the drilled hole 16 and-casing 14 is shown filled with cement l8. Inserted into the cavern through casing 14 is production tube 20.

The cavern can be used to store a. fluid. such as a hydrocarbon or ammonia. Normally, the fluid will be gaseous in nature but will exist in the cavern as a liquid.

To remove the storedfluid, a second fluid, more dense than and immiscible with the stored fluid, is admitted to the cavern through production tube 20 and holes 22. The second fluid, usually water or brine, displaces the stored fluid from the cavern into annular space 24, formed by casing 14 and production tube 20. The displaced fluid is removed at the surface using suitable means not shown.

To store a fluid in the cavern, the process described above is reversed. The fluid to be stored is pumped through annular space 24 into the cavern to displace the heavier fluid from the cavern through production tube 20.

As shown in FIG. 1, production tube 20 is unprotected and subject to severe damage and even severance by debris falling from ceiling 26. The manner in which this problem issolved'is shown in FIG. 2.

Referring now to FIG. 2, there is shown about the production tube a mound 28 of comminuted material such as crushed rock or other suitable material. Crushed rock is preferred because of its steep angle of repose and its ready availability. The mound preferably extends from the bottom of the cavern to the ceiling in order to afford maximum protection to production tube 20.

The comminuted material may vary in size over a wide range. It should not be so finely divided as to inhibit introduction of the denser fluid into the cavern or its removal from the cavern through production tube 20. Material having a particle size of A to 1 inch is suitable. A uniform particle size within the range of onehalf to three-fourths inch is particularly desirable. Unifonn particles provide more void space for storage of fluids within mound 28.

Any convenient way of introducing the comminuted material into the cavern and forming the mound will be suitable. A preferred way of doing this is to dump the comminuted material into the cavern through annular space 24. The falling material will assume its normal angle of repose and form a mound about the production tube. The manner in which mound 28 affords protection to production tube 20 can be seen by referring to FIG. 3. FIG. 3 shows the result of a major cave-in occurring in cavern 10. The ceiling of the cavern has risen to 26. The old ceiling 26 is shown as a broken line. Fallen debris 30 now covers the bottom of the cavern. Mound 28 has prevented the debris from damaging production tube 20. Thus, this tube still extends to the original bottom of the cavern. The storage capacity of the cavern is retained as stored fluid or the heavier displacing fluid can readily penetrate the voids in the fallen debris. Had the production tube been severed, or otherwise damaged so as to require replacement, a new tube would extend only to the top of the fallen debris, thus causing a loss in storage capacity. To restore full capacity, a hole would have to be drilled through the fallen debris to the original bottom of the cavern and a new production tube inserted. Either of these alternatives would have economic consequences not suffered if this invention is employed. These and other advantages of this invention can be readily appreciated by one skilled in the art.

I claim:

1. In a cavern for storing fluids, the method of protecting a tube extending into the cavern from damage by falling debris comprising: (1) extending said tube through a hole from the surface of the earth into said cavern, said hole of sufficiently greater diameter than said tube to form an annulus around said tube; (2) introducing comminuted material from the surface of the earth into the cavern thereby forming a protective mound of the material about the tube.

2. A method according to claim 1 wherein the mound extends from the bottom of the cavern to the ceiling of the cavern.

3. A method according to claim 1 wherein the comminuted material is crushed rock.

4. A method according to claim 3 wherein the crushed rock has an average particle size of A to 1 inch.

5. A method according to claim 3 wherein the crushed rock has an average particle size of one-half to three-fourths inch.

6. A method according to claim 1 wherein the comminuted material is introduced into the cavern through an annular space formed by the tube and a casing surrounding the tube, said casing extending from the ceiling of the cavern to the surface.

7. In combination with an underground cavern penetrated by a drilled hole, a hollow tube extending from the surface of the earth to the bottom of said cavern, a casing surrounding said tube extending from said surface to the ceiling of the cavern and defining an annular space between the casing and the tube, and a mound of comminuted material about the tube extending from the bottom to the ceiling of the cavern.

8. A combination according to claim 7 wherein the comminuted material is crushed rock. 

1. In a cavern for storing fluids, the method of protecting a tube extending into the cavern from damage by falling debris comprising: (1) extending said tube through a hole from the surface of the earth into said cavern, said hole of sufficiently greater diameter than said tube to form an annulus around said tube; (2) introducing comminuted material from the surface of the earth into the cavern thereby forming a protective mound of the material about the tube.
 2. A method according to claim 1 wherein the mound extends from the bottom of the cavern to the ceiling of the cavern.
 3. A method according to claim 1 wherein the comminuted material is crushed rock.
 4. A method according to claim 3 wherein the crushed rock has an average particle size of 1/4 to 1 inch.
 5. A method according to claim 3 wherein the crushed rock has an average particle size of one-half to three-fourths inch.
 6. A method according to claim 1 wherein the comminuted material is introduced into the cavern through an annular space formed by the tube and a casing surrounding the tube, said casing extending from the ceiling of the cavern to the surface.
 7. In combination with an underground cavern penetrated by a drilled hole, a hollow tube extending from the surface of the earth to the bottom of said cavern, a casing surrounding said tube extending from said surface to the ceiling of the cavern and defining an annular space between the casing and the tube, and a mound of comminuted material about the tube extending from the bottom to the ceiling of the cavern.
 8. A combination according to claim 7 wherein the comminuted material is crushed rock. 